The present invention relates to a granular material supply system for a closed system and, more particularly, to a granular material supply system including a pressure case, a conveying means disposed in the pressure case, and a weighing means for weighing the granular powder being conveyed by the conveying means when necessary, and combined with a delivery unit for delivering granular powder supplied thereto by a granular powder supply unit.
Various plants including smelting reduction steelmaking plants, direct reduction steelmaking plants, coal gasification plants and vacuum degassing plants produce a poisonous gas or an inflammable gas or supplies a poisonous gas or an inflammable gas into a reaction furnace. Such a plant uses a granular material supply system capable of supplying a granular material into the reaction furnaces without opening the plant into the environment.
The inventors of the present invention proposed a granular material supply system 100 to be applied to a smelting reduction steelmaking plant. As shown in FIG. 8, this previously proposed granular material supply system 100 includes, as principal components, a granular material loading unit 101, a granular material supply hopper 102, a vibrating feeder 103, load cells 104 for weighing the granular material supply hopper 102 containing a granular material, and a chute 105. The granular material, such as granular powder iron ore or coal, is loaded through the granular material loading unit 101 into the granular material supply hopper 102, the granular material supply hopper 102 containing the granular material is weighed, the vibrating feeder 103 carries the granular material to the chute 105, and then the granular material is supplied through the chute 105 into a processing unit, such as a furnace.
In the granular material supply system 100, a loading line 110 provided with a stop valve 111 and a metal expansion joint 112 connects the granular material loading unit 101 and the granular material supply hopper 102, a discharge line 113 provided with a rubber expansion joint 114 connects the granular material supply hopper 102 and the vibrating feeder 103, and a feed line 115 provided with a rubber expansion joint 116 and a stop valve 117 connects the vibrating feeder 103 and the chute 105.
The load cells 104 weigh the sum of the weight of the granular material supply hopper 102 and that of the granular material contained in the granular material supply hopper 102. Therefore the metal expansion joint 112 is indispensable and the load cells 104 need to support the granular material supply hopper 102. The vibrating feeder 103 has one end part held through the rubber expansion joint 114 by the granular material supply hopper 102. The rubber expansion joints 114 and 116 absorb vibrations of the vibrating feeder 103. A gas line 121 provided with an equalizing valve 120 has one end connected to the granular material supply hopper 102 and the other end connected to the vibrating feeder 103. When weighing the granular material supply hopper 102 and the granular material contained in the granular material supply hopper 102, the respective pressures in the granular material supply hopper 102 and the vibrating feeder 103 are equalized to prevent the reduction of weighing accuracy.
When supplying a granular material from a granular material supply hopper 130 through chutes 133 and 134 to two granular material receiving units 131 and 132 at a fixed distance of, for example, about 40 m, the chutes 133 and 134 must be inclined at a fixed inclination to a horizontal plane of, for example about 50xc2x0 to enable the granular material to fall smoothly through the chutes 133 and 134. Consequently, the granular material supply hopper 130 must be installed on a level at several tens meters, for example, about 50 m, above the ground.
In a granular material weighing and conveying system disclosed in JP-U No. Hei 7-34023, a weighing tank is supported on a load cell, a base placed on a fixed body is supported on a bellows under the weighing tank, the bellows and the weighing tank are connected by a pressure line and the pressure in the weighing tank is regulated by an equalizing valve to weigh the granular material by the load cell so that weighing accuracy may not be reduced.
A fixed-quantity granular material feed method disclosed in JP-A No. Sho 54-129684 weighs a granular material while the same is being conveyed from a plurality of granular material storage tanks by belt conveyors. This method is not intended for feeding a granular material to a pressure unit without opening a closed system to the external environment.
The aforesaid granular material supply system 100 needs the metal expansion joint to weight the granular material supply hopper 102 containing the granular material, needs the rubber expansion joints 114 and 116 to absorb the vibrations of the vibrating feeder 103 and needs the gas line 121 provided with the equalizing valve 120 to prevent the reduction of weighing accuracy. Consequently, the granular material supply system 100 is complicated in construction, is large and requires large equipment investment.
Measurement of the sum of the weight of the granular material supply hopper 102 and that of the granular material contained in the granular material supply hopper 102 reduces weighing accuracy. Particularly, weighing error is very large when the capacity of the granular material supply hopper 102 large. For example, if the capacity of the granular material supply hopper 102 is 500 tons and weighing accuracy is 0.5%, weighing error is as large as 2.5 tons. The vibrations of the vibrating feeder 103 reduce weighing accuracy.
The rubber expansion joints 114 and 116 must be capable of withstanding vibrations exerted thereon by the vibrating feeder 103 to prevent the leakage of gases from the granular material supply system. However, it is impossible to prevent the leakage of gases through the rubber expansion joints 114 and 116 perfectly. The use of rubber expansion joints 114 and 116 deficient in durability causes serious problems particularly when the gases are inflammable or poisonous.
When supplying a granular material from the single granular material supply hopper 130 to the two furnaces 131 and 132 as shown in FIG. 9, the granular material supply hopper 130 must be installed on a high level and the chutes 133 and 134 connecting the granular material supply hopper 130 to the two furnaces 131 and 132 are very long. Consequently, this granular material supply system including the chutes 133 and 134 needs a large space for installation and a very large equipment investment.
It is an object of the present invention to simplify the construction of a granular material supply system for a closed system, to enhance the weighing accuracy of the granular material supply system, to enhance the airtightness of the granular material supply system, to reduce the size of the granular material supply system and space for installation and to enhance the economical advantage of the granular material supply system.
According to a first aspect of the present invention, a granular material supply system for supplying a granular material to a granular material using apparatus included in a closed system without opening the closed system to the external environment comprises a granular material supply unit holding a granular material, and a granular material feed unit that receives the granular material from the granular material supply unit and feeds the same, wherein the granular material feed unit includes a pressure case provided with an inlet connected to the granular material supply unit and an outlet for feeding the granular material, and a conveying means disposed in the pressure case to convey the granular material received through the inlet to the outlet.
The conveying means may be a belt conveyor, the pressure case may be a pressure vessel, and the conveying means may be provided with a weighing means for weighing the granular material.
The granular material supply system is capable of supplying the granular material to the granular material using apparatus without opening the closed system to the external environment. Therefore, the granular material supply system is applicable to various plants including smelting reduction steelmaking plants, direct reduction steelmaking plants, coal gasification plants and vacuum degassing plants.
The belt conveyor is disposed in the pressure case, the granular material is supplied from the granular material supply unit through the inlet into the pressure case, and the granular material is conveyed by the belt conveyor to the outlet and is supplied through the outlet into the granular material using apparatus.
Whereas the prior art granular material supply system needs to measure the sum of the weight of the granular material supply hopper 102 and the granular material contained in the granular material supply hopper 102, the granular material supply system of the present invention does not need to do so and the weight of the granular material can be measured in the pressure case. Therefore the pressure case may be immovable, any special joints, such as expansion joints, are not necessary for connecting the inlet and the outlet of the pressure case to the granular material supply unit and the granular material using apparatus, respectively. Consequently, the granular material supply system is very simple in construction and the leakage of gases through the joints can be perfectly prevented. The use of the belt conveyor for conveying the granular material reduces vibration and noise greatly. Granular material feed rate can be adjusted by adjusting the conveying speed of the conveying means and the supply of the granular material into the granular material using apparatus can be stopped by stopping the conveying means.
In the granular material supply system according to the first aspect of the present invention, the conveying means may include a belt conveyor. The simple and small construction of the belt conveyor are advantages of the belt conveyor when disposing the belt conveyor in the pressure case and when weighing the granular material while the same is being conveyed. In this granular material supply system, the granular material delivered through the inlet onto the belt conveyor is conveyed, and the outlet is formed below a delivery end of the belt conveyor.
In the granular material supply system according to the first aspect of the present invention, the pressure case may be a pressure vessel including a cylindrical body and a pair of end plates closing the opposite ends of the cylindrical body, and capable of withstanding positive or negative pressure. The pressure case, i.e., the pressure vessel, is excellent in airtightness and pressure tightness, is resistant to breakage, has structural advantages and can be formed in a small size.
According to the first aspect of the present invention, a weighing means may be disposed in the pressure case to weigh the granular material being conveyed by the conveying means. The weighing means may be, for example, a load cell. When the conveying means includes the belt conveyor, one or some of carrier rollers included in the belt conveyor are supported on load cells to weigh the granular material while the same is being conveyed. Since the weighing means measure the weight of the granular material together with that of only relatively light components of the belt conveyor, the granular material can be weighed in a greatly improved weighing accuracy.
In the granular material supply system according to the first aspect of the present invention, the conveying means may include a belt conveyor having a plurality of carrier rollers and a conveyor belt supported on the carrier rollers, the granular material supplied onto the belt conveyor through the inlet may be conveyed by the belt conveyor, and the weighing means may weigh the granular material on a part of the conveyor belt between the two adjacent carrier rollers disposed at positions other than those directly below the inlet. The part of the conveyor belt between the two adjacent carrier rollers can be regarded as a rigid part independent of a part of the same directly below the inlet. Thus a fixed amount of the granular material on the part of the conveyor belt between the two adjacent carrier rollers can be weighed by the weighing means without weighing the granular material being supplied through the inlet onto the part of the conveyor belt directly below the inlet. The total weight of the granular material conveyed by the belt conveyor can be easily determined on the basis of a value measured by the weighing means and time for which the granular material is conveyed.
The granular material supply system according to the first aspect of the present invention may be provided with a gas blowing means for blowing an inert gas into the pressure case to carry the granular material fallen off the conveying means in the pressure case or to purge the pressure case of gases. The gas blown into the pressure case carries the granular material fallen off the conveying means in the pressure case toward the outlet to prevent the accumulation of the granular material fallen off the conveying means. The gas blown into the pressure case purges the pressure case of gases.
In the granular material supply system according to the first aspect of the present invention, the granular material supply unit includes one granular material supply hopper, a granular material supply line provided with a stop valve means may be connected to a lower part of the granular material supply hopper. The granular material contained in the granular material supply hopper is supplied through the granular material supply line and the inlet into the pressure case when the stop valve means is opened. The supply of the granular material from the granular material supply hopper into the pressure case is stopped when the stop valve means is closed. In a state where the stop valve is closed, gases contained in the granular material supply hopper is replaced with an inert gas to permit an external loading means to load the granular material supply hopper with the granular material.
In the granular material supply system according to the first aspect of the present invention, the granular material supply unit may include a plurality of granular material supply hoppers, the pressure case may be provided with a plurality of inlets connected to the plurality of granular material supply hoppers, respectively, and granular material supply lines each provided with a stop valve means may be connected to lower parts of the granular material supply hoppers, respectively. The granular material contained in each granular material supply hopper is supplied through the associated granular material supply line and the associated inlet into the pressure case when the associated stop valve means is opened. The supply of the granular material from each granular material supply hopper into the pressure case is stopped when the associated stop valve means is closed. In a state where the stop valve is closed, gases contained in each granular material supply hopper is replaced with an inert gas to permit an external loading means to load the granular material supply hopper with the granular material.
The plurality of granular material supply hoppers may contain granular materials of different kinds, respectively. All or some of the granular materials of different kinds are supplied into the pressure case, and the conveying means conveys the same toward the outlet to feed the same into the granular material using apparatus.
In the granular material supply system according to the first aspect of the present invention, a feed line connected to the outlet of the pressure case may be provided with a stop valve means. The granular material can be fed through the outlet into the granular material using apparatus when the stop valve means is opened. The granular material supply system can be disconnected from the granular material using apparatus by closing the stop valve means. In a state where the stop valve means of the feed line is closed, the gases contained in the granular material supply hopper can be replaced with an inert gas to permit an external loading means to load the granular material supply hopper with the granular material.
In the granular material supply system according to the first aspect of the present invention, the granular material supply hopper may be provided with a gas discharging means for discharging gases from the granular material supply hopper, and a purging gas blowing means for blowing a purging gas into the granular material supply hopper. In a state where the flow of the granular material through inlet or the outlet of the pressure case is prevented by the stop valve means, the gases contained in the granular material supply hopper can be replaced with an inert gas by blowing the purging gas into the granular material supply hopper by the purging gas blowing means and discharging the gases from the granular material supply hopper by the gas discharging means, and the granular material supply hopper can be charged with the granular material.
According to a second aspect of the present invention, a granular material supply system for a closed system, for supplying granular materials to a granular material using apparatus included in the closed system without opening the closed system to the external environment comprises a plurality of granular material supply units for holding and supplying granular materials of a plurality of kinds, a common pressure case provided with a plurality of inlets connected to the plurality of granular material supply units, respectively, and at least one outlet through which the granular materials are fed, and a common conveying means disposed in the common pressure case to convey the granular materials delivered thereto through the plurality of inlets to the outlet, wherein each of the granular material supply units includes a hopper for holding the granular material, a pressure case provided with an inlet connected to a granular material supply line connected to the hopper, and an outlet connected to the inlet of the common pressure case, and a conveying means disposed in the pressure case to convey the granular material delivered thereto to the outlet.
Basically, the plurality of hoppers of the plurality of granular material supply units contain granular materials of different kinds, respectively. In each granular material supply unit, the conveying means disposed in the pressure case is operated to receive the granular material through the inlet into the pressure case. Granular material supply rate can be adjusted by adjusting the conveying speed of the conveying means, and the feed of the granular material can be stopped by stopping the conveying means. Accordingly, all or some of the granular materials of the plurality of kinds can be delivered to the common conveying means disposed in the common pressure case at desired supply rates, respectively, the granular materials can be conveyed to the outlet by the common conveying means and can be fed to the granular material using apparatus. The granular material supply system is capable of supplying the granular materials to the granular material using apparatus without opening the closed system to the external environment. Therefore, the granular material supply system is applicable to various plants including smelting reduction steelmaking plants, direct reduction steelmaking plants, coal gasification plants and vacuum degassing plants.
In this granular material supply system, the pressure case of each granular material supply unit may be immovable, any special joints, such as expansion joints, are not necessary for connecting the inlet and the outlet of the pressure case to the hopper and inlet of the common pressure case, the common pressure case may be immovable, and any special joints, such as expansion joints are not necessary for connecting the outlet of the common pressure case to the granular material using apparatus.
Thus, the granular material supply system is very simple in construction, and the pressure cases and the common pressure case are not very tall. Therefore the granular material supply system has a relatively small height, which is advantageous in respect of space for installation. Leakage of gasses through the joints can be surely prevented. Since the granular material is conveyed by the conveying means in each pressure case and the granular materials are conveyed by the common conveying means in the common pressure case, noise and vibration generated by the conveying means can be greatly reduced.
Each granular material supply unit may be provided with a weighing means for weighing the granular material being conveyed by the conveying means in the pressure case, each inlet or outlet may be provided with a stop valve means, the outlet of the common pressure case may be provided with a stop valve means. The common pressure case may be provided with outlets in opposite end parts thereof, respectively, and the common conveying means may be capable of conveying the granular materials selectively in the normal or the reverse direction.
In the granular material supply system according to the second aspect of the present invention, the common conveying means and the conveying means may be belt conveyors. The belt conveyors can be formed in simple, small construction, which facilitates the installation of the belt conveyors in the common pressure case and the pressure cases and weighing the granular materials in the pressure cases or in the common pressure case.
In the granular material supply system according to the second aspect of the present invention, the common pressure case may be a pressure vessel having a cylindrical body and a pair of end plates closing the opposite ends of the cylindrical body. The pressure case, i.e., the pressure vessel, is excellent in airtightness and pressure tightness, is resistant to breakage, has structural advantages and can be formed in a small size.
In the granular material supply system according to the second aspect of the present invention, each of the pressure case may be a pressure vessel having a cylindrical body and a pair of end plates closing the opposite ends of the cylindrical body. The pressure case, i.e., the pressure vessel, is excellent in airtightness and pressure tightness, is resistant to breakage, has structural advantages and can be formed in a small size.
According to the second aspect of the present invention, a weighing means may be installed in each of the pressure cases to weigh the granular material being conveyed by the conveying means. The weighing means may be, for example, a load cell. When the conveying means includes the belt conveyor, one or some of carrier rollers included in the belt conveyor are supported on load cells to weigh the granular material while the same is being conveyed. Since the weighing means measure the weight of the granular material together with that of only relatively light components of the belt conveyor and is capable of weighing the granular material without being affected by the pressure of a gas, the granular material can be weighed in a greatly improved weighing accuracy.
In the granular material supply system according to the second aspect of the present invention, the common pressure case may be provided with outlets in opposite end parts thereof and the common conveying means may be capable of conveying the granular materials selectively in the normal or reverse direction. The common conveying means is operated to convey the granular materials in the normal direction to one of the outlets and the same is operated to convey the granular materials in the reverse direction to the other outlet. Thus, the granular materials can be supplied selectively to one or the other of two granular material using apparatuses.
The granular material supply system according to the second aspect of the present invention may be provided with a filtering means capable of sucking and collecting fine particles produced in the common pressure case. Fine particles are produced in the vicinity of the outlet of the common pressure case when the granular materials are dropped from the common conveying means. The fine particles deposit gradually in the bottom of the common pressure case unless the common pressure case is cleaned periodically. Since the filtering means capable of sucking and collecting fine particles is combined with the common pressure case, fine particles deposit scarcely in the common pressure case. A gas or air sucked together with fine particles and cleaned by the filtering means may be returned into the common pressure case. The granular material supply system may share the filtering means with other granular material supply systems.